The present invention relates to medical devices in general, and in particular, to rotational atherectomy devices.
One of the most common types of vascular diseases afflicting Americans today involves the narrowing of blood vessels by plaque or other materials. Left untreated, such narrowed vessels can contribute to high blood pressure, strokes, or cardiac arrest.
One of the most common techniques for treating a fully or partially blocked vessel is to bypass the blockage with a healthy vessel obtained from elsewhere in the body. A less traumatic approach involves the insertion of a balloon angioplasty device into the vessel and expanding the balloon to compress the occlusion against the vessel wall. Another minimally invasive technique is an atherectomy procedure, where a high-speed cutting device such as the Rotoblator(trademark), produced by SCIMED Life Systems, Inc., the U.S. assignee of the present invention, is inserted into the vessel and advances against the occlusion in order to grind it into small particles that are passed by the body.
In many instances, a physician will place a stent in the area of the treated occlusion. In the case of balloon angioplasty, stents operate to prevent the compressed occlusion from springing back to its former size. For vessels that have undergone an atherectomy procedure, the stent helps maintain an open passage or lumen through the vessel.
Regardless of the procedure used, a fair percentage of stents become re-occluded within a relatively short period of time. However, the material that occludes the stent is somewhat different from the occluding material that blocked the vessel in the first instance. Therefore, techniques used to treat an original occlusion are not believed to be as effective when treating a re-occluded stent. Therefore, there is a need for a device and method of effectively treating re-occluded stents in a manner that does minimal or no damage to the stent itself.
The present invention is a system and method for removing occluding material from a stent that is positioned within a vessel. In one embodiment of the invention, a rotational cutter is made of a material having a hardness less than or equal to the hardness of the material used to make the stent. The cutter has a number of recessed blades such that the outer surface of the cutter is relatively smooth and cutting is limited to tissue that enters channels in which the blades are placed. The cutter is preferably routed on a guide wire that is shaped such that the cutter is pressed radially outward against the inner surface of the stent. To aid in the removal of ablated material that is cut from the stent, an aspiration system including a catheter coupled to a source of negative pressure operates to aspirate ablated particles.
In another embodiment of the invention, a cutting mechanism includes a catheter with a self-expanding stent on the distal end thereof. One or more knives are secured to the stent such that the knives are pushed radially outward by the stent. Once the expanding stent is positioned in an occluded stent, the one or more knives are extended and rotated to remove occluding material. Ablated material from the occluded stent is preferably aspirated from the vessel.
In another embodiment of the invention, a cutting mechanism includes a helically-wound cutter that surrounds an inflatable balloon. The balloon is inflated to urge the cutter radially outward against the inner wall of the stent. Ablated particles removed from the stent are preferably aspirated from the vessel.